Antiglare film and process for producing the same

ABSTRACT

Disclosed are an antiglare film having a high level of anti-scintillation properties, high sharpness of transmitted images, high light transmittance (total light transmittance), and a high level of external light reflection preventive properties, and a process for producing the antiglare film. A resin and non-agglomerative particles having a specific particle diameter are selected so that the difference in refractive index between the resin and the particles is 0.05 to 0.15. The resin and the non-agglomerative particles are brought to a coating composition using, as a solvent, a good solvent for the resin and a poor solvent for the resin. The coating composition is coated onto a substrate film to form a coating which is then dried. In the course of the drying, as the amount of the good solvent in the coating decreases, the poor solvent acts to cause the gelation of the particles and the resin. Thus, good concaves and convexes can be advantageously formed on the surface of the coating. The layer thus formed can meet various property requirements for antiglare films.

This is a Continuation of application Ser. No. 10/747,227 filed Dec. 30,2003, which in turn is a Division of U.S. Ser. No. 09/576,241 filed May24, 2000. The entire disclosures of the prior applications are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

This invention relates to an antiglare film which, when disposed on thefront of CRTs (cathode ray tubes) displays or liquid crystal displays,serves to diffuse light externally incident on these displays, therebyreducing glare.

BACKGROUND ART

In CRT displays, accelerated electrons collide with phosphors located onthe inner side of the front glass to impart energy to the phosphors.This permits the phosphors to emit light, and, in general, red, green,and blue lights outgo on the front side. In liquid crystal displays, theliquid crystal per se does not emit light. Since, however, light isapplied from the backside to enhance the visibility of liquid crystalimages, on the whole of the display, light is emitted toward the front.

When the display is used in a room, light from lighting equipment, suchas a fluorescent lamp, enters the surface of the display and isreflected from the display surface. This causes glaring of the displayscreen or reflection of a fluorescent lamp on the display screen, makingit difficult to perceive letters and the like displayed on the screen.

The disposition of an antiglare film, having a light diffusing layerformed by coating a silica-containing resin coating composition onto atransparent substrate film, on the front of the display to diffuseexternal light causative of glare, and consequently to alleviate theglare of the display screen, has been already carried out in the art.

Conventional antiglare films include one wherein concaves and convexeshave been formed on the surface of a light diffusing layer through theagglomeration of particles of agglomerative silica or the like, onewherein resin beads having a larger particle diameter than the thicknessof the coating have been added to impart concaves and convexes on thesurface of the coating, and one wherein an embossing film havingconcaves and convexes on its surface had been laminated onto the surfaceof an unsolidified coating to transfer the shape of concaves andconvexes onto the surface of the coating followed by the separation ofthe embossing film.

All the above conventional antiglare films have light diffusingproperties, a certain level of antiglare effect, and, in addition, byvirtue of the thin film form, can be easily applied to displays.

However, when light emitted from the display toward the front is passed,through the antiglare film, shining called “scintillation” occurs on thefilm surface, disadvantageously posing a problem of deterioratedvisibility of displayed images.

The following properties are important for an antiglare film which, inuse, is disposed on the front of a display: (1) high level ofanti-scintillation properties; (2) high image sharpness; (3) high lighttransmittance (=total light transmittance); and (4) high antiglareproperties derived from light diffusing properties (=high level ofcapability of preventing the reflection of external light from afluorescent lamp or the like (external light reflection preventiveproperties)). None of the conventional antiglare films simultaneouslysatisfy all the above property requirements.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide anantiglare film simultaneously satisfying all of the propertyrequirements, that is, (1) high anti-scintillation properties, (2) highsharpness of transmitted images, (3) high total light transmittance, and(4) high external light reflection preventive properties withoutsignificantly altering the form of the conventional antiglare film, thatis, the thin film form, and a process for producing the same.

The present inventors have found that, in the formation of an antiglarefilm by coating of a resin coating composition with particles dispersedtherein, the formation of good concaves and convexes and the provisionof an antiglare film satisfying various properties required of lightdiffusing films can be realized by a method which comprises the stepsof: selecting a resin and non-agglomerative particles having a specificparticle diameter so that the difference in refractive index between theresin and the particles is 0.05 to 0.15; bringing the resin and thenon-agglomerative particles to a coating composition using, as asolvent, a good solvent for the resin and a poor solvent for the resin;coating the coating composition onto a substrate film to form a coating;and drying the coating, whereby, in the course of the drying, as theamount of the good solvent contained in the coating decreases, the poorsolvent acts to cause the gelation of the particles and the resin.

According to one aspect of the present invention, there is provided anantiglare film comprising at least a light diffusing resin layer formedof non-agglomerative light-transparent fine particles dispersed in alight-transparent resin, the light-transparent fine particles having aparticle diameter of 1.0 to 5.0 μm, the difference in optical refractiveindex between the light-transparent fine particles and thelight-transparent resin being 0.05 to 0.15, the content of thelight-transparent fine particles being 5 to 30 parts by weight based on100 parts by weight of the light-transparent resin, the surfaceroughness of the light diffusing resin layer being 0.12 to 0.30 in termsof center line average roughness (Ra) and 1.0 to 2.9 in terms often-point average roughness (Rz).

In another embodiment of the antiglare film according to the presentinvention, the light diffusing resin layer is stacked on a transparentsubstrate.

According to the present invention, the thickness of the light diffusingresin layer is preferably 1 to 3 times the diameter of thelight-transparent fine particles.

According to the present invention, the antiglare film preferably has animage sharpness of 80 to 300 and a level of external light reflectionpreventive properties of 5 to 70.

According to another preferred embodiment of the present invention, thelight-transparent resin is a cured product of an ionizingradiation-curable resin.

According to another aspect of the present invention, there is provideda process for producing an antiglare film, comprising the steps of:

providing a coating composition comprising non-agglomerativelight-transparent fine particles, a light-transparent resin, a goodsolvent for the light-transparent resin, and a poor solvent for thelight-transparent resin, the light-transparent fine particles having aparticle diameter of 1.0 to 5.0 μm, the difference in optical refractiveindex between the light-transparent fine particles and thelight-transparent resin being 0.05 to 0.15, said ingredients beingcontained in the coating composition in an amount of 5 to 30 parts byweight for the light-transparent fine particles based on 100 parts byweight of the light-transparent resin and in an amount of 20 to 1,000parts by weight for the solvent in terms of the total amount of the goodsolvent and the poor solvent, the parts by weight ratio of the goodsolvent to the poor solvent being 100:20 to 100:70;

coating the coating composition onto a substrate; and

then drying the coating to reduce the weight ratio of the good solventto the light-transparent resin, whereby, while allowing thelight-transparent fine particles and the light-transparent resin to gel,the coating is solidified to create concaves and covexes on the surfaceof the coating.

According to a preferred embodiment of the present invention, thelight-transparent resin and the good and poor solvents are selected fromthe following combinations:

(a) a combination of an acrylate resin, a good solvent for the acrylateresin selected from the group consisting of toluene, methyl ethylketone, ethyl acetate, n-butyl acetate, and cyclohexanone, and a poorsolvent for the acrylate resin selected from the group consisting ofmethanol, ethanol, n-butanol, and isopropanol;

(b) a combination of a cellulosic resin, a good solvent for thecellulosic resin selected from the group consisting of ethyl acetate,n-butyl acetate, acetone, and cyclohexanone, and a poor solvent for thecellulosic resin selected from the group consisting of methanol,ethanol, n-butanol, and isopropanol;

(c) a combination of an epoxy resin, a good solvent for the epoxy resinselected from the group consisting of methanol/toluene (“/” referring tomixing), ethanol/xylene, methyl ethyl ketone, ethyl acetate, n-butylacetate, and methyl isobutyl ketone, and a poor solvent for the epoxyresin selected from the group consisting of toluene, xylene,cyclohexanone, and cyclopentane;

(d) a combination of a urea melamine resin, a good solvent for the ureamelamine resin selected from the group consisting of ethyl acetate,n-butyl acetate, n-butanol, and n-hexyl alcohol, and a poor solvent forthe urea melamine resin selected from the group consisting of tolueneand xylene; and

(e) a combination of a urethane resin, a good solvent for the urethaneresin selected from the group consisting of ethyl acetate, n-butylacetate, and methyl ethyl ketone, and a poor solvent for the urethaneresin selected from the group consisting of methanol and ethanol.

In the above process, the drying is preferably carried out at atemperature of 20 to 100° C.

According to another embodiment of the process, the light-transparentresin is an ionizing radiation-curable resin and, after the formation ofconcaves and convexes on the surface of the coating, an ionizingradiation is applied to the coating to cure the coating throughcrosslinking.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of the antiglare film according to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described withreference to FIG. 1. An antiglare film 1 according to the presentinvention basically has a laminate structure comprising a transparentsubstrate 2 and a light diffusing resin layer 3 stacked on thetransparent substrate 2. The light diffusing resin layer 3 internallycontains light-transparent fine particles 4 and has fine concaves andconvexes 5 on its surface.

In the formation of the light diffusing resin layer 3 by coating, thetransparent substrate 2 is an object to be coated with the lightdiffusing resin layer 3 and thus is in most cases necessary.Alternatively, a casting method may be used which comprises providing areleasable substrate instead of the transparent substrate 2, coating alight diffusing resin layer 3 on the surface of the releasablesubstrate, and then separating the releasable substrate from the lightdiffusing resin layer 3. According to the casting method, aself-supporting light diffusing resin layer 3 not provided with thetransparent substrate 2 can be obtained.

Materials for constituting the antiglare film according to the presentinvention, the mixing ratio of the materials, the surface roughness ofthe antiglare film, solvents (good solvent and poor solvent) used in theproduction of the antiglare film according to the present invention,drying and the like will be successively described.

The non-agglomerative light-transparent fine particles constituting theantiglare film according to the present invention have an opticalrefractive index very close to the light-transparent resin which will bedescribed next, and, thus, when dispersed in the light-transparentresin, are transparent. The diameter of the light-transparent fineparticles is preferably in the range of 1.0 to 5.0 μm. When the particlediameter is less than 1.0, the addition of the light-transparent fineparticles to the light-transparent resin does not provide satisfactorylight diffusing properties. On the other hand, when the particlediameter exceeds 5.0 μm, the image sharpness and the light transmittanceare unsatisfactory.

Specific examples of non-agglomerative light-transparent fine particlesusable herein include organic non-agglomerative light-transparent fineparticles, such as styrene beads (refractive index 1.60), melamine beads(refractive index 1.57), acryl beads (refractive index 1.49),acryl-styrene beads (refractive index 1.54), polycarbonate beads,polyethylene beads, and polyvinyl chloride beads. Among them, styrenebeads and acryl-styrene beads are preferred.

Among the non-agglomerative light-transparent fine particles, inorganicnon-agglomerative light-transparent fine particles usable herein includefine particle of SiO₂ (refractive index 1.5 to 2.0), Al—SiO₂ (refractiveindex 1.65), and GeO₂ (refractive index 1.65). Among them, fineparticles of SiO₂ are preferred.

Since all the above light-transparent fine particles arenon-agglomerative, the difference in refractive index between thelight-transparent fine particles and the light-transparent resin caneffectively offer internal scattering properties, and thus can preventscintillation.

Light-transparent resins include a crosslinking-cured product of anionizing radiation-curable resin, a cured product prepared bycrosslinking of an ionizing radiation-curable resin together with asolvent evaporation type resin, particularly a thermoplastic resin, anda cured product of a thermosetting resin.

Among them, resins belonging to the category of ionizingradiation-curable resins are mainly acrylate oligomers or prepolymers,or monofunctional or polyfunctional monomers. Oligomers or prepolymersinclude relatively low-molecular weight polyester resin, polyetherresin, acrylic resin, epoxy resin, urethane resin, alkyd resin,spiroacetal resin, polybutadiene resin, and polythiol-polyene resin andacrylate or methacrylate (acrylate and methacrylate being hereinaftercollectively referred to as “(meth)acrylate”) of polyhydric alcohols orthe like.

These ionizing radiation-curable resins may contain the followingmonofunctional monomers or polyfunctional monomers as a reactivediluent. Monofunctional monomers include ethyl (meth)acrylate,ethylhexyl (meth)acrylate, styrene, methylstyrene, and N-pyrrolidone,and polyfunctional monomers include trimethylolpropanetri(meth)acrylate, hexanediol (meth)acrylate, tripropylene glycoldi(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritoltri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, and neopentyl glycol di(meth)acrylate. Thesemonofunctional monomers or polyfunctional monomers may be cured as suchby crosslinking without the oligomer or the prepolymer, or alternativelymay be used as a mixture thereof with a thermoplastic resin or athermosetting resin.

Preferred solvent evaporation type resins, which may be added to theionizing radiation-curable resin, are mainly cellulosic resins becauseof high transparency, and examples thereof include nitrocellulose resin,acetylcellulose resin, cellulose acetate propionate resin, andethylhydroxyethylcellulose resin.

Thermosetting resins usable as the light-transparent resin includephenolic resins, urea resins, diallyl phthalate resins, melamine resins,guanamine resins, unsaturated polyester resins, polyurethane resins,epoxy resins, aminoalkyd resins, urea-melamine resins, and siliconeresins.

When the thermosetting resin is used, if necessary, for example, acrosslinking agent or a polymerization initiator may be added.

In the antiglare film according to the present invention, the differencein optical refractive index between the light-transparent fine particlesand the light-transparent resin should be 0.05 to 0.15. Regarding therefractive index of the light-transparent resin, the ionizingradiation-curable resin has a refractive index of about 1.5. In the caseof other resins, when the optical refractive index is low, therefractive index difference is sometimes larger than the acceptablerefractive index difference. This sometimes results in loweredtransparency of the light-transparent fine particles. In this case, fineparticles having high optical refractive index, for example, fineparticles of TiO₂ (refractive index 2.3 to 2.7), Y₂O₃ (refractive index1.87), La₂O₃ (refractive index 1.95), ZrO₂ (refractive index 2.05), orAl₂O₃ (refractive index 1.63) may be added to the light-transparentresin to enhance the refractive index of the light-transparent resin,thereby regulating the difference in refractive index between thelight-transparent resin and the light-transparent fine particles.

The non-agglomerative light-transparent fine particles are added in anamount of 5 to 30 parts by weight based on 100 parts by weight of thelight-transparent resin. When the amount of the non-agglomerativelight-transparent fine particles added is less than 5 parts by weight,satisfactory light diffusing properties cannot be provided. Therefore,the anti-scintillation properties and the external light reflectionpreventive properties of the antiglare film are unsatisfactory. When theamount of the non-agglomerative light-transparent fine particles addedexceeds 30 parts by weight, the light-diffusing properties can beimproved. In this case, however, the haze is increased resulting inlowered sharpness of transmitted images, and, in addition, the lighttransmittance (=total light transmittance) is unfavorably lowered.

The antiglare film according to the present invention preferably has thefollowing specified surface roughness. Specifically, the center lineaverage roughness (Ra) is 0.12 to 0.30, and the ten-point averageroughness (Rz) is 1.0 to 2.9. The center line average roughness (Ra) andthe ten-point average roughness (Rz) may be determined according to themethods specified in JIS B 0601.

Here the center line average roughness (Ra) is 0.12 to 0.30, and theten-point average roughness (Rz) is 1.0 to 2.9.

In the antiglare film according to the present invention, the thicknessof the light diffusing resin layer is preferably 1 to 3 times thediameter of the light-transparent fine particles internally dispersed inthe light diffusing resin layer. The antiglare film according to thepresent invention is produced by the process of the present invention,described below, using a good solvent and a poor solvent, and concavesand convexes are formed on the surface of the coating through amechanism of drying in the course of the production process. Therefore,even though the layer thickness clearly exceeds the diameter of the fineparticles to such an extent that the fine particles are internallyembedded in the light diffusing resin layer, the antiglare film can havethe surface roughness specified above.

When the thickness of the light diffusing resin layer is smaller thanthe diameter of the light-transparent fine particles internallydispersed in the light diffusing resin layer, the concaves and convexesformed on the layer surface are large, leading to deterioratedanti-scintillation properties. On the other hand, when the thickness ofthe light diffusing resin layer is more than 3 times the diameter of thelight-transparent fine particles, increasing the amount of the fineparticles added is necessary for forming concaves and convexes havinggood shape on the surface of the layer. This increases the haze andconsequently lowers the sharpness of transmitted images and the totallight transmittance.

According to the antiglare film of the present invention, specifying theparticle diameter of the light-transparent fine particles, thedifference in refractive index between the light-transparent fineparticles and the light-transparent resin, the mixing ratio between thelight-transparent fine particles and the light-transparent resin, andthe surface roughness can provide excellent properties of the antiglarefilm, that is, a level of sharpness of transmitted images of 80 to 300and a level of external light reflection preventive properties of 5 to70.

The sharpness (distinctness) of a transmitted image is determinedaccording to JIS K 7105. Specifically, light transmitted through orreflected by a sample is measured through a moving optical comb by usinga measuring apparatus for the sharpness of an image, and the sharpnessof the transmitted image is calculated from the results by the followingequation:C=(M−m)/(M+m)×100wherein

C represents sharpness of transmitted image, %;

M represents maximum wave height; and

m represents minimum wave height.

The larger the value of the sharpness C (%) of the transmitted image,the higher the sharpness of the image and the better the quality of theimage. The apparatus used is an image clarity measuring apparatus(ICM-1DP) manufactured by Suga Test Instruments Co., Ltd. In the opticalcomb, four slit widths are used. Therefore, the maximum value is100%×4=400%.

The level of the external light reflection preventive properties may bemeasured as follows. A black pressure-sensitive adhesive tape is appliedto a light diffusing resin layer on its side not having concaves andconvexes as a sample to prevent the reflection of light from thebackside. While this sample is kept horizontal, a parallel light fluxhaving a size of 5 mm square is applied to the sample at an angle of 10degrees to the normal thereof. The light flux reflected on the lightdiffusing resin layer in its side having concaves and convexes isobserved from the regular reflection direction by means of a CCD camera.The aperture of the CCD camera is regulated to bring the luminance ofthe peak to a given value, and the inclination angle of the luminance atthe inflection point of the luminance in the edge portion of thereflected light flux. This inclination angle is regarded as the level ofexternal light reflection preventive properties. When a light flux isreflected on a specular surface, the inclination of the luminance issubstantially equal to 90 degrees. In the case of a matte surface havinglarge concaves and convexes, the inclination of the luminance issmaller.

The “external light reflection” in the item of evaluation of antiglarefilms prepared in examples and comparative examples described belowrefers to the level of external light reflection preventive propertiesdetermined in this way.

In the production of the antiglare film according to the presentinvention, non-agglomerative light-transparent fine particles are mixedwith a light-transparent resin, the mixture is dispersed or dissolved ina solvent composed of a good solvent for the light-transparent resin anda poor solvent for the light-transparent resin to prepare a coatingcomposition, and the coating composition is coated onto a substrate toform a coating which is then dried to cure the coating.

In the coating composition, the solvent (the good solvent and the poorsolvent being collectively referred to as “solvent”) is used in anamount of 20 to 1,000 parts by weight based on 100 parts by weight ofthe light-transparent resin. In this case, the parts by weight ratio ofthe good solvent to the poor solvent in the solvent is 100:20 to 100:70.

The term “good solvent” refers to a solvent having an excellentcapability of dissolving or swelling the resin, and the term “poorsolvent” refers to a solvent which has a poor capability of dissolvingthe resin and is likely to cause the gelation of the resin. In thisconnection, the following matter should be noted. Both a suitable goodsolvent and a suitable poor solvent vary depending upon each resin asthe solute. Further, probably, whether the solubility is excellent orpoor is relatively determined. Examples of combinations of typicallight-transparent resins with good and poor solvents for thelight-transparent resins include:

(a) a combination of an acrylate resin, a good solvent for the acrylateresin selected from the group consisting of toluene, methyl ethylketone, ethyl acetate, n-butyl acetate, and cyclohexanone, and a poorsolvent for the acrylate resin selected from the group consisting ofmethanol, ethanol, n-butanol, and isopropanol;

(b) a combination of a cellulosic resin, a good solvent for thecellulosic resin selected from the group consisting of ethyl acetate,n-butyl acetate, acetone, and cyclohexanone, and a poor solvent for thecellulosic resin selected from the group consisting of methanol,ethanol, n-butanol, and isopropanol;

(c) a combination of an epoxy resin, a good solvent for the epoxy resinselected from the group consisting of methanol/toluene (“/” referring tomixing), ethanol/xylene, methyl ethyl ketone, ethyl acetate, n-butylacetate, and methyl isobutyl ketone, and a poor solvent for the epoxyresin selected from the group consisting of toluene, xylene,cyclohexanone, and cyclopentane;

(d) a combination of a urea melamine resin, a good solvent for the ureamelamine resin selected from the group consisting of ethyl acetate,n-butyl acetate, n-butanol, and n-hexyl alcohol, and a poor solvent forthe urea melamine resin selected from the group consisting of tolueneand xylene; and

(e) a combination of a urethane resin, a good solvent for the urethaneresin selected from the group consisting of ethyl acetate, n-butylacetate, and methyl ethyl ketone, and a poor solvent for the urethaneresin selected from the group consisting of methanol and ethanol.

In the above combinations, two or more good solvents and/or two or morepoor solvents may be used for the light-transparent resin.

In the coating composition, the amount of the solvent is 20 to 1,000parts by weight based on 100 parts by weight of the light-transparentresin. When the resin or monomer used has high solubility, the amount ofthe solvent may be small. On the other hand, when the resin or monomerused has relatively low solubility or, upon dissolution in the solvent,forms a highly viscous solution, the amount of the solvent used isincreased.

When the amount of the solvent used is below the lower limit of thespecified amount range, upon the evaporation of only a small amount ofthe solvent, the viscosity is increased or otherwise gelation occurs.This is a source of trouble in the production of the antiglare film. Onthe other hand, when the amount of the solvent used is above the upperlimit of the specified amount range, much energy is required for theevaporation of the solvent to dry the coating.

The parts by weight ratio of the good solvent to the poor solvent in thesolvent is 100:20 to 100:70.

A coating composition, wherein the amount of the poor solvent used isbelow the lower limit of the specified amount range, is disadvantageousin that, since the major proportion of the solvent is accounted for bythe good solvent, upon coating of the coating composition, the wholesolvent rapidly disappears making it difficult for concaves and convexesto be formed on the surface of the coating by mere drying. On the otherhand, when the poor solvent is contained in an amount larger than theupper limit of the specified amount range, gelation proceeds in an earlystage. This is likely to result in the formation of large concaves andconvexes. Further, in this case, there is a fear of the coatingcomposition causing gelation during storage, and, in addition, when theevaporation rate of the poor solvent is slow, there is a possibilitythat the coating is less likely to be dried.

The relative evaporation rate R of the solvent may be used as a measureof evaporation rate of the solvent. The relative evaporation rate R ofthe solvent A is determined using, as a standard, the time required forn-butyl acetate to be evaporated at room temperature, and calculated bythe equation R=[time required for n-butyl acetate to beevaporated]/[time required for solvent A to be evaporated]. The largerthe value of R, the higher the evaporation rate, and the smaller thevalue of R, the lower the evaporation rate.

Preferably, the relative evaporation rate R is not more than 3.7 for thegood solvent, and not more than 1.9 for the poor solvent. The goodsolvent and the poor solvent are preferably selected so that therelative evaporation rate R of the good solvent is higher than that ofthe poor solvent. Since, however, the good solvent and the poor solventshould also be selected by taking into consideration the parts by weightratio of the good solvent to the poor solvent and the capacity of adryer for drying after coating of the coating composition, the relativeevaporation rate R of the good solvent selected is in some cases lowerthan that of the poor solvent.

When the coating composition satisfies a requirement such that theamount of the solvent (the good solvent and the poor solvent beingcollectively referred to as “solvent”) is 20 to 1,000 parts by weightbased on 100 parts by weight of the light-transparent resin and theparts by weight ratio of the good solvent to the poor solvent in thesolvent is 100:20 to 100:70, this coating composition is free fromgelation during storage and other problems, and can maintain a viscositysuitable for coating.

Materials for the substrate to be coated with the coating composition inthe formation of the light diffusing resin layer include transparentglass and transparent resins. The transparent resin may be in the formof a film, a sheet, or a plate.

An example of transparent resin is a resin wherein hydroxyl groups ofcellulose have been partially or entirely esterified mainly with a lowerfatty acid. Specific examples of such resins include acetylcellulose andcellulose acetate butyrate, typically cellulose triacetate. Further,various polyesters (typically polyethylene terephthalate=PET), acryl(typically polymethyl methacrylate), polyurethane, polycarbonate,polymethylpentene, (meth)acrylonitrile, polyethersulfone, polysulfone,polyetherketone and the like may also be used.

Among them, a film of the transparent resin is more preferred becausethe film of the transparent resin can permit continuous coating, canprovide a flexible antiglare film which is highly compatible withvarious applications. The film thickness of the transparent resin isgenerally 25 to 100 μm.

As described above, when the substrate to be coated with the coatingcomposition has a releasable surface, upon the formation of the lightdiffusing resin layer, the substrate may be separated from the lightdiffusing resin layer to provide a self-supporting light diffusing resinlayer not having any substrate. In some cases, the substrate inherentlyhas poor adhesion to the light diffusing resin layer due to therelationship between the material for the substrate and the material forthe light diffusing resin layer. In this case, there is no need tointentionally render the surface of the substrate releasable.Alternatively, when the formation of the self-supporting light diffusingresin layer is contemplated, a method may also be used wherein thecoating composition is coated onto a specular surface of a metal or thelike to form a layer followed by the separation of the layer from thespecular surface or the like.

The coating composition may be coated onto the substrate by aconventional coating or printing method. Examples of coating andprinting methods include: coating methods, such as roll coating, gravureroll coating, spray coating, curtain flow coating, flow coating, kisscoating, roll coating using a spinner-whirler or the like, and brushcoating; and printing methods, such as gravure printing and silk screenprinting.

When drying is carried out after coating onto the substrate, concavesand convexes are formed on the surface of the coating as the dryingproceeds.

As soon as the coating composition is coated onto the substrate by thecoating or printing method, drying is initiated. To this end, it iscommon practice to perform blowing of air and/or heating. Under theseconditions, the solvent is gradually evaporated.

As the amount of the solvent contained in the coating compositionconstituting the wet coating decreases, the light-transparent resin,present near the surface, which has been in the state of dissolutionowing to the action of the good solvent, begins to gel due to thepresence of the poor solvent. This leads to the formation of a solidcomprised of the light-transparent resin and the light-transparent fineparticles around the surface of the coating. In the gelation, the higherthe evaporation rate of the good solvent as compared with the poorsolvent, the higher the drying temperature, or the larger the flow ofair blown, the higher the rapidity in reduction of the solvent and thehigher the rapidity in the formation of the solid comprised of thelight-transparent resin and the light-transparent fine particles whichresult in the formation of relatively large concaves and convexes. Onthe other hand, when the evaporation rate of the good solvent is notvery higher than that of the poor solvent or when drying conditions aremilder, the speed of reduction in the solvent contained in the coatingcomposition is lower. In this case, relatively fine concaves andconvexes are formed.

Further, the smaller the amount of the good solvent contained in thecoating composition, the higher the rapidity in gelation. In this case,relatively large concaves and convexes are formed.

That is, according to the production process of the present invention,the size of concaves and convexes formed on the surface of the coatingcan be regulated by regulating the difference in evaporation ratebetween the good solvent and the poor solvent, drying conditions, andthe proportion of the good solvent in the solvent. Since the concavesand convexes on the surface of the coating are not governed by the sizeof the light-transparent fine particles, different size levels ofconcaves and convexes can be advantageously formed even whenlight-transparent fine particles having the same size are used.

While retaining the concaves and convexes formed on the surface of thecoating, the coating can be solidified by continuing the drying, orcured by a suitable method according to the resin component in thecoating composition used. Specifically, in the case of a thermosettingresin, if necessary, heat is further applied, and, in the case of anionizing radiation-curable resin, an ionizing radiation is applied toperform curing through crosslinking.

EXAMPLES Example 1

The following materials were thoroughly mixed together according to thefollowing formulation to prepare a coating composition for a lightdiffusing resin layer. Light-transparent resin 100 pts. wt.Pentaerythritol triacrylate (PET 30, manufactured by Nippon Kayaku Co.,Ltd.) Photoinitiator 5 pts. wt. (Irgacure 184, manufactured byCIBA-GEIGY Ltd.) Light-transparent fine particles 8 pts. wt. Polystyreneresin filler (particle diameter 1.3 μm, refractive index 1.6) Goodsolvent 60 pts. wt. Methyl isobutyl ketone (relative evaporation rate R1.6) Poor solvent 15 pts. wt. Isobutyl alcohol (relative evaporationrate R 0.64)

A cellulose triacetate film (TD-80U, thickness 80 μm, manufactured byFuji Photo Film Co., Ltd.) was provided as a substrate. The coatingcomposition prepared above was roll coated onto one side of thesubstrate. The coating was then dried at a temperature of 50° C. to formconcaves and convexes on the surface of the coating, followed byapplication of ultraviolet light at 120 mJ to cure the coating. Thus, anantiglare film was prepared.

Examples 2 to 7 and Comparative Examples 1 to 5

For Examples 2 to 7 and Comparative Examples 1 to 4, in the coatingcomposition used, the light transparent resin and photoinitiator usedand amounts thereof were the same as used in Example 1, and the lighttransparent fine particles and the solvent were varied. The otherconditions were the same as those used in Example 1, except that thelayer thickness and the drying temperature were varied.

For Comparative Example 5, only pentaerythritol triacrylate was coatedonto an embossing film having concaves and convexes on its surface to athickness of 3 μm to form a coating which was then cured and separated.

The difference between Example 1 and the other examples and thecomparative examples and the like are shown in Tables 1 and 2 below.TABLE 1 Light transparent fine particles: Material Good solvent: Poorsolvent: Layer Particle diameter/refractive Name Name thickness Ex.index/amount in pts. wt. R/amount in pts. wt. R/amount in pts. wt.Drying temp. Ex. 1 Polystyrene Methyl isobutyl Isobutanol 3 μm 1.3/1.6/8pts. wt. ketone 0.64/15 pts. wt. 50° C. 1.6/60 pts. wt. Ex. 2 Same asEx. 1 Same as Ex. 1 Same as Ex. 1 3 μm 70° C. Ex. 3 Same as Ex. 1 Sameas Ex. 1 except Same as Ex. 1 except Same as that the amount was thatthe amount was Ex.1 changed to 52.5 changed to 22.5 pts. wt. pts. wt.Ex. 4 {circle around (1)} Polystyrene n-Butyl acetate Isopropanol 3 μm1.3/1.6/4 pts. wt. 1.0/60 pts. wt. 1.5/40 pts. wt. 70° C. {circle around(2)} Polystyrene 1.5/1.55/4 pts. wt. Ex. 5 Polystyrene Toluene Ethanol 5μm 3.5/1.6/12 pts. wt. 2.0/40 pts. wt. 1.54/35 pts. wt. 80° C. Ex. 6Polystyrene Cyclohexanone Isopropanol 8 μm 5/1.6/8 pts. wt. 0.32/65 pts.wt. 1.5/35 pts. wt. 60° C. Ex. 7 Polystyrene Xylene n-Butanol 8 μm4/1.6/9 pts. wt. 0.76/40 pts. wt. 0.47/35 pts. wt. 100° C.

TABLE 2 Light transparent fine particles: Material Good solvent: Poorsolvent: Layer Comp. Particle diameter/refractive Name Name thicknessEx. index/amount in pts. wt. R/amount in pts. wt. R/amount in pts. wt.Drying temp. Comp. Same as Ex. 1 Methyl isobutyl 3 μm Ex. 1 ketone 70°C. 1.6/75 pts. wt. Comp. Same as Ex. 1 Isobutanol 3 μm Ex. 2 0.64/75pts. wt. 70° C. Comp. {circle around (1)} Agglomerative silica Toluene 3μm Ex. 3 1.2/1.45/3 pts. wt. 2.0/75 pts. wt. 70° C. {circle around (2)}Agglomerative silica 1.7/1.45/3 pts. wt. Comp. Agglomerative silicaIsobutanol 3 μm Ex. 4 1.7/1.45/6 pts. wt. 0.64/75 pts. wt. 70° C. Comp.3 μm Ex. 5 50° C.

The antiglare films prepared in the examples and the comparativeexamples were evaluated, and the results are shown in Tables 3 and 4.

In Tables 3 and 4, the “scintillation” was determined by putting a colorfilter (staggered grid arrangement or triangular arrangement, pitch 150μm; in order to avoid the influence of color, the color filter consistsof black matrix only and the filter on each pixel is not colored) on abacklight for a liquid crystal display (LIGHTBOX 45, manufactured byHAKUBA) and fixing the antiglare film to a position distant by 160 μmfrom the surface of the color filter in such a manner that the antiglarefilm on its side having concaves and convexes was on the viewer side,and inspecting the surface of the film by means of a CCD camera todetermine the standard deviation of a variation in luminance. TABLE 3Ex. No. Item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Transmittance91.2 91 91.2 91.5 91 91.4 91 Haze 13.3 15 19.3 8.6 24.7 14 16 Internalhaze 5 5 5 3.5 9 6 6.5 Scintillation 10 12 13 14 9 12 11 Sharpness 124100 80 139 157 95 107 External light reflection 60 53 26 56 36 45 51preventive properties Ra 0.174 0.185 0.197 0.167 0.186 0.230 0.191 θ a2.33 2.15 2.68 2.04 3.45 2.24 2.09 Rz 1.19 1.67 2.21 1.76 2.19 2.78 1.97Rmax 1.31 2.14 3.14 1.83 2.31 2.93 2.46 Sm 40.0 52.6 50.8 47.6 48.8 4055

-   Sharpness: Sharpness of transmitted image. The larger the value, the    better the sharpness.-   External light reflection preventive properties: The smaller the    value, the better the properties.

Transmittance: Total light transmittance. TABLE 4 Ex. No. Comp. Comp.Comp. Comp. Comp. Item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Transmittance 91.789 91.2 90.6 92.3 Haze 17 45 11 21 4.5 Internal haze 15 3 0.3 0.3 0Scintillation 9 14 19 14 41 Sharpness 325 15.9 40 32 276 External light87 3.5 45 19 80 reflection preventive properties Ra 0.105 1.40 0.3280.365 0.111 θ a 0.94 5.11 2.20 3.44 1.1 Rz 0.38 7.72 2.93 3.01 0.64 Rmax0.41 11.5 3.16 3.53 0.75 Sm 131 118 42.1 53.7 89.3

-   Sharpness: Sharpness of transmitted image. The larger the value, the    better the sharpness.-   External light reflection preventive properties: The smaller the    value, the better the properties.-   Transmittance: Total light transmittance.

Example 1 is different from Example 2 only in drying temperature. Theantiglare film of Example 1 using a lower drying temperature, ascompared with the antiglare film of Example 2, had finer concaves andconvexes and, by virtue of this, possessed better scintillation andsharpness of transmitted image (the sharpness of transmitted image beinghereinafter and in tables referred to simply as “sharpness”). Theantiglare film of Example 2 using a higher drying temperature, ascompared with the antiglare film of Example 1, had higher surfaceroughness. Due to the higher surface roughness, the level of externallight reflection preventive properties was better although the sharpnesswas lower and the haze was somewhat higher.

In Example 3, the proportion of the poor solvent was higher than that inExample 1. Due to the higher proportion of the poor solvent, despite thefact that the drying temperature in Example 3 was the same as that inExample 1, the surface roughness was higher than that in the case ofExample 2 using a higher drying temperature than Example 1. Therefore,the level of external light reflection preventive properties was furtherimproved, although the sharpness was lower and the haze was higher.

In Example 4, 50% of the fine particles used was accounted for by fineparticles having a refractive index of 1.5 which was close to therefractive index of the resin. Due to the lower haze, the sharpness wassomewhat higher. Although the level of scintillation was inferior tothat in Example 1 due to lower internal haze, this level ofscintillation was satisfactory from the practical point of view.

In Examples 5 to 7 wherein the diameter of fine particles and thesolvent were varied, the properties of the antiglare films were as goodas those in Example 1 and other examples.

In Comparative Example 1 wherein the solvent consisted of the goodsolvent alone, concaves and convexes were less likely to be formed onthe surface and, consequently, the surface was substantially flat. Thisprovided inferior external light reflection preventive properties,although the scintillation and the sharpness were good.

In Comparative Example 2 wherein the solvent consisted of the poorsolvent alone, considerably large concaves and convexes were formed toconstitute a frosted glass-like surface. This results in lowered lighttransmittance and very low sharpness.

In Comparative Example 3, the sharpness was poor although thescintillation and the external light reflection preventive propertieswere good.

In Comparative Example 5 wherein, unlike the examples and the othercomparative examples, an embossing film was used to form concaves andconvexes and the fine particles were not added, the absence of the fineparticles provided good transmittance and sharpness. However, thescintillation and the level of the external light reflection preventiveproperties were not satisfactory.

According to the present invention wherein the light-transparent resinand the light-transparent fine particles in a resin layer and thesurface roughness of the resin layer were specified, an antiglare filmhaving such a resin layer possesses excellent properties, that is,possesses a high level of anti-scintillation properties, a high level ofsharpness of transmitted images, and high light transmittance (=totallight transmittance) while enjoying a high level of external lightreflection preventive properties.

According to a preferred embodiment of the present invention, theantiglare film is provided with a transparent substrate. Thisconstruction can advantageously offer good strength and goodhandleability at the time of production and fabrication.

According to the present invention, unlike the prior art, the thicknessof the resin coating is larger than the diameter of the fine particles.Therefore, the antiglare film is durable.

Further, according to the present invention, sharp images can beprovided on a display using this antiglare film, and the visibility ofimages is satisfactory even under an environment exposed to externallight or under illumination. Further, according to a preferredembodiment of the present invention, the resin layer is formed of acrosslinking-cured product of an ionizing radiation-curable resincomposition. The antiglare film having this resin layer possessesexcellent physical and chemical properties.

According to the production process of the present invention, anantiglare film having desired concaves and convexes can be produced byproperly selecting good and poor solvents, mixing ratio, dryingtemperature and other conditions, without necessarily limiting thediameter of fine particles to be incorporated.

Further, according to a preferred embodiment of the present invention, asolvent may be selected from highly general-purpose solvents to producethe antiglare film.

According to the production process of the present invention, anantiglare film having excellent physical and chemical properties can bestably produced by forming concaves and convexes using an ionizingradiation-curable resin and applying an ionizing radiation to thecoating to cure the coating through crosslinking.

1) An antiglare film comprising a light diffusing resin layer formed ofnon-agglomerative light-transparent fine particles dispersed in alight-transparent resin, thereby obtaining internal scatteringproperties to prevent scintillation. 2) The antiglare film according toclaim 1, wherein the difference in optical refractive index between thelight-transparent fine particles and the light-transparent resin is 0.05to 0.15.